Todd...Get em mounted and take to the car wash and wash away all the old paint. If you like pre-soak them with some simple green or similar product. Makes the paint come off easier. Next go to the craft store and get some water based acrylic paint. I forget the brand but it comes in a tube and the color is Titanium White. Also purchase a good quality flat brush. For them to look GREAT it takes about three coats and patience. Use a black sharpie to touch up areas where you get over the line a little...........but honestly I have never done it as my loving wife takes care of it. I take the wheels off the car and roll them into the living room so she can be comfortable. It takes her about 6 hours to do all 4 and you can ask anyone in our club about my tires as they always look perfect and crisp. You can add additional coats during the year when they need it and still look good. I completely strip them about once a year right before we go to Austin for our annual event. Hope this helps.
Gary
Here is a picture
http://www.erareplicas.com/cars/morris291/index.htm